Sorry to be the bearer of bad news AG3, but you are incorrect. Overdrive is one more gear. Drive is the 4/3 gears availble to you for normal driving. If you are pulling a heavy load, you would down shift in a manual transmition, so in the case of an automatic, Overdrive would be useless. It's meant for high RPM and low Torque. Lower gears are for higher torque. hig torgeue is needed when pulling large loads.